Semiconductor chip assembly with post/base heat spreader and vertical signal routing

ABSTRACT

A semiconductor chip assembly includes a semiconductor device, a heat spreader, a substrate and an adhesive. The semiconductor device is electrically connected to the substrate and thermally connected to the heat spreader. The heat spreader includes a post and a base. The post extends upwardly through an opening in the adhesive into an aperture in the substrate, and the base extends laterally and supports the substrate. The adhesive extends between the post and the substrate and between the base and the substrate. The substrate includes first and second conductive layers and a dielectric layer therebetween, and the assembly provides vertical signal routing between a pad at the first conductive layer and a terminal below the adhesive.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. application Ser. No.12/406,510 filed Mar. 18, 2009, which claims the benefit of U.S.Provisional Application Ser. No. 61/071,589 filed May 7, 2008, U.S.Provisional Application Ser. No. 61/071,588 filed May 7, 2008, U.S.Provisional Application Ser. No. 61/071,072 filed Apr. 11, 2008, andU.S. Provisional Application Ser. No. 61/064,748 filed Mar. 25, 2008,each of which is incorporated by reference.

This application also claims the benefit of U.S. Provisional ApplicationSer. No. 61/150,980 filed Feb. 9, 2009, which is incorporated byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to semiconductor chip assembly, and moreparticularly to a semiconductor chip assembly with a semiconductordevice, a substrate, an adhesive and a heat spreader and its method ofmanufacture.

2. Description of the Related Art

Semiconductor devices such as packaged and unpackaged semiconductorchips have high voltage, high frequency and high performanceapplications that require substantial power to perform the specifiedfunctions. As the power increases, the semiconductor device generatesmore heat. Furthermore, the heat build-up is aggravated by higherpacking density and smaller profile sizes which reduce the surface areato dissipate the heat.

Semiconductor devices are susceptible to performance degradation as wellas short life span and immediate failure at high operating temperatures.The heat not only degrades the chip, but also imposes thermal stress onthe chip and surrounding elements due to thermal expansion mismatch. Asa result, the heat must be dissipated rapidly and efficiently from thechip to ensure effective and reliable operation. A high thermalconductivity path typically requires heat conduction and heat spreadingto a much larger surface area than the chip or a die pad it is mountedon.

Light emitting diodes (LEDs) have recently become popular alternativesto incandescent, fluorescent and halogen light sources. LEDs provideenergy efficient, cost effective, long term lighting for medical,military, signage, signal, aircraft, maritime, automotive, portable,commercial and residential applications. For instance, LEDs providelight sources for lamps, flashlights, headlights, flood lights, trafficlights and displays.

LEDs include high power chips that generate high light output andconsiderable heat. Unfortunately, LEDs exhibit color shifts and lowlight output as well as short lifetimes and immediate failure at highoperating temperatures. Furthermore, LED light output and reliabilityare constrained by heat dissipation limits. LEDs underscore the criticalneed for providing high power chips with adequate heat dissipation.

LED packages usually include an LED chip, a submount, electricalcontacts and a thermal contact. The submount is thermally connected toand mechanically supports the LED chip. The electrical contacts areelectrically connected to the anode and cathode of the LED chip. Thethermal contact is thermally connected to the LED chip by the submountbut requires adequate heat dissipation by the underlying carrier toprevent the LED chip from overheating.

Packages and thermal boards for high power chips have been developedextensively in the industry with a wide variety of designs andmanufacturing techniques in attempts to meet performance demands in anextremely cost-competitive environment.

Plastic ball grid array (PBGA) packages have a chip and a laminatedsubstrate enclosed in a plastic housing and are attached to a printedcircuit board (PCB) by solder balls. The laminated substrate includes adielectric layer that often includes fiberglass. The heat from the chipflows through the plastic and the dielectric layer to the solder ballsand then the PCB. However, since the plastic and the dielectric layertypically have low thermal conductivity, the PBGA provides poor heatdissipation.

Quad-Flat-No Lead (QFN) packages have the chip mounted on a copper diepad which is soldered to the PCB. The heat from the chip flows throughthe die pad to the PCB. However, since the lead frame type interposerhas limited routing capability, the QFN package cannot accommodate highinput/output (I/O) chips or passive elements.

Thermal boards provide electrical routing, thermal management andmechanical support for semiconductor devices. Thermal boards usuallyinclude a substrate for signal routing, a heat spreader or heat sink forheat removal, pads for electrical connection to the semiconductor deviceand terminals for electrical connection to the next level assembly. Thesubstrate can be a laminated structure with single layer or multi-layerrouting circuitry and one or more dielectric layers. The heat spreadercan be a metal base, a metal slug or an embedded metal layer.

Thermal boards interface with the next level assembly. For instance, thenext level assembly can be a light fixture with a printed circuit boardand a heat sink. In this instance, an LED package is mounted on thethermal board, the thermal board is mounted on the heat sink, thethermal board/heat sink subassembly and the printed circuit board aremounted in the light fixture and the thermal board is electricallyconnected to the printed circuit board by wires. The substrate routeselectrical signals to the LED package from the printed circuit board andthe heat spreader spreads and transfers heat from the LED package to theheat sink. The thermal board thus provides a critical thermal path forthe LED chip.

U.S. Pat. No. 6,507,102 to Juskey et al. discloses an assembly in whicha composite substrate with fiberglass and cured thermosetting resinincludes a central opening, a heat slug with a square or rectangularshape resembling the central opening is attached to the substrate atsidewalls of the central opening, top and bottom conductive layers areattached to the top and bottom of the substrate and electricallyconnected to one another by plated through-holes through the substrate,a chip is mounted on the heat slug and wire bonded to the top conductivelayer, an encapsulant is molded on the chip and solder balls are placedon the bottom conductive layer.

During manufacture, the substrate is initially a prepreg with B-stageresin placed on the bottom conductive layer, the heat slug is insertedinto the central opening and on the bottom conductive layer and spacedfrom the substrate by a gap, the top conductive layer is mounted on thesubstrate, the conductive layers are heated and pressed towards oneanother so that the resin melts, reflows into the gap and solidifies,the conductive layers are patterned to form circuit traces on thesubstrate and expose the excess resin flash on the heat slug, and theexcess resin flash is removed to expose the heat slug. The chip is thenmounted on the heat slug, wire bonded and encapsulated.

The heat flows from the chip through the heat slug to the PCB. However,manually dropping the heat slug into the central opening isprohibitively cumbersome and expensive for high volume manufacture.Furthermore, since the heat slug is difficult to accurately position inthe central opening due to tight lateral placement tolerance, voids andinconsistent bond lines arise between the substrate and the heat slug.The substrate is therefore partially attached to the heat slug, fragiledue to inadequate support by the heat slug and prone to delamination. Inaddition, the wet chemical etch that removes portions of the conductivelayers to expose the excess resin flash also removes portions of theheat slug exposed by the excess resin flash. The heat slug is thereforenon-planar and difficult to bond to. As a result, the assembly suffersfrom high yield loss, poor reliability and excessive cost.

U.S. Pat. No. 6,528,882 to Ding et al. discloses a thermal enhanced ballgrid array package in which the substrate includes a metal core layer.The chip is mounted on a die pad region at the top surface of the metalcore layer, an insulating layer is formed on the bottom surface of themetal core layer, blind vias extend through the insulating layer to themetal core layer, thermal balls fill the blind vias and solder balls areplaced on the substrate and aligned with the thermal balls. The heatfrom the chip flows through the metal core layer to the thermal balls tothe PCB. However, the insulating layer sandwiched between the metal corelayer and the PCB limits the heat flow to the PCB.

U.S. Pat. No. 6,670,219 to Lee et al. discloses a cavity down ball gridarray (CDBGA) package in which a ground plate with a central opening ismounted on a heat spreader to form a thermal dissipating substrate. Asubstrate with a central opening is mounted on the ground plate using anadhesive with a central opening. A chip is mounted on the heat spreaderin a cavity defined by the central opening in the ground plate andsolder balls are placed on the substrate. However, since the solderballs extend above the substrate, the heat spreader does not contact thePCB. As a result, the heat spreader releases the heat by thermalconvection rather than thermal conduction which severely limits the heatdissipation.

U.S. Pat. No. 7,038,311 to Woodall et al. discloses a thermal enhancedBGA package in which a heat sink with an inverted T-like shape includesa pedestal and an expanded base, a substrate with a window opening ismounted on the expanded base, an adhesive attaches the pedestal and theexpanded base to the substrate, a chip is mounted on the pedestal andwire bonded to the substrate, an encapsulant is molded on the chip andsolder balls are placed on the substrate. The pedestal extends throughthe window opening, the substrate is supported by the expanded base andthe solder balls are located between the expanded base and the perimeterof the substrate. The heat from the chip flows through the pedestal tothe expanded base to the PCB. However, since the expanded base mustleave room for the solder balls, the expanded base protrudes below thesubstrate only between the central window and the innermost solder ball.Consequently, the substrate is unbalanced and wobbles and warps duringmanufacture. This creates enormous difficulties with chip mounting, wirebonding and encapsulant molding. Furthermore, the expanded base may bebent by the encapsulant molding and may impede soldering the package tothe next level assembly as the solder balls collapse. As a result, thepackage suffers from high yield loss, poor reliability and excessivecost.

U.S. Patent Application Publication No. 2007/0267642 to Erchak et al.discloses a light emitting device assembly in which a base with aninverted T-like shape includes a substrate, a protrusion and aninsulative layer with an aperture, electrical contacts are mounted onthe insulative layer, a package with an aperture and a transparent lidis mounted on the electrical contacts and an LED chip is mounted on theprotrusion and wire bonded to the substrate. The protrusion is adjacentto the substrate and extends through the apertures in the insulativelayer and the package into the package, the insulative layer is mountedon the substrate, the electrical contacts are mounted on the insulativelayer and the package is mounted on the electrical contacts and spacedfrom the insulative layer. The heat from the chip flows through theprotrusion to the substrate to a heat sink. However, the electricalcontacts are difficult to mount on the insulating layer, difficult toelectrically connect to the next level assembly and fail to providemulti-layer routing.

Conventional packages and thermal boards thus have major deficiencies.For instance, dielectrics with low thermal conductivity such as epoxylimit heat dissipation, whereas dielectrics with higher thermalconductivity such as epoxy filled with ceramic or silicon carbide havelow adhesion and are prohibitively expensive for high volumemanufacture. The dielectric may delaminate during manufacture orprematurely during operation due to the heat. The substrate may havesingle layer circuitry with limited routing capability or multi-layercircuitry with thick dielectric layers which reduce heat dissipation.The heat spreader may be inefficient, cumbersome or difficult tothermally connect to the next level assembly. The manufacturing processmay be unsuitable for low cost, high volume manufacture.

In view of the various development stages and limitations in currentlyavailable packages and thermal boards for high power semiconductordevices, there is a need for a semiconductor chip assembly that is costeffective, reliable, manufacturable, versatile, provides flexible signalrouting and has excellent heat spreading and dissipation.

SUMMARY OF THE INVENTION

The present invention provides a semiconductor chip assembly thatincludes a semiconductor device, a heat spreader, a substrate and anadhesive. The semiconductor device is electrically connected to thesubstrate and thermally connected to the heat spreader. The heatspreader includes a post and a base. The post extends upwardly throughan opening in the adhesive into an aperture in the substrate, and thebase extends laterally from the post. The adhesive extends between thepost and the substrate and between the base and the substrate. Thesubstrate includes first and second conductive layers and a dielectriclayer therebetween and the assembly provides vertical signal routing.

The assembly can provide the vertical signal routing between a pad atthe first conductive layer and a terminal below the adhesive using arouting line at the second conductive layer, a first via that extendsthrough the dielectric layer to the routing line, and a second via thatextends through the adhesive to the routing line.

In accordance with an aspect of the present invention, a semiconductorchip assembly includes a semiconductor device, an adhesive, a heatspreader and a substrate. The adhesive includes an opening. The heatspreader includes a post and a base, wherein the post is adjacent to thebase and extends above the base in an upward direction, and the baseextends below the post in a downward direction opposite the upwarddirection and extends laterally from the post in lateral directionsorthogonal to the upward and downward directions. The substrate includesa pad, a routing line, a first via and a dielectric layer, wherein thepad extends above the dielectric layer, the routing line extends belowthe dielectric layer, the first via extends through the dielectric layerto the routing line, and an aperture extends through the substrate.

A second via extends through the adhesive to the routing line, aterminal extends below the adhesive, and an electrically conductive pathbetween the pad and the terminal includes the first via, the routingline and the second via.

The semiconductor device is above and overlaps or is below andoverlapped by the post, is electrically connected to the pad and theterminal, and is thermally connected to the post and the base.

The adhesive is mounted on and extends above the base, extends into agap in the aperture between the post and the substrate, extends acrossthe dielectric layer in the gap and is sandwiched between the post andthe dielectric layer and between the base and the substrate.

The substrate is mounted on the adhesive and extends above the base, andthe routing line is embedded in the adhesive.

The post extends through the opening into the aperture and above thedielectric layer, and the base extends below the adhesive and thesubstrate.

The heat spreader can include a cap that is above and adjacent to andcovers in the upward direction and extends laterally in the lateraldirections from a top of the post. For instance, the cap can have arectangular or square shape and the top of the post can have a circularshape. The cap can also contact and cover a portion of the adhesive thatis coplanar with and adjacent to the post. The cap can also be coplanarwith the pad above the dielectric layer. In addition, the post canthermally connect the base and the cap. The heat spreader can be copperand consist of the post, the base and the cap. Alternatively, the heatspreader can consist of the post and the base. In either case, the heatspreader provides heat dissipation and spreading from the semiconductordevice to the next level assembly.

The semiconductor device can extend above and overlap the post, beelectrically connected to the pad and thereby electrically connected tothe terminal, and be thermally connected to the cap and therebythermally connected to the base. For instance, the semiconductor devicecan be a semiconductor chip that is mounted on the cap using a dieattach, electrically connected to the pad using a wire bond andthermally connected to the cap using the die attach.

Alternatively, the semiconductor device can extend below the base and beoverlapped by the post, be electrically connected to the terminal andthereby electrically connected to the pad, and be thermally connected tothe base and thereby thermally connected to the cap. For instance, thesemiconductor device can be a semiconductor chip that is mounted on thebase using a die attach, electrically connected to the terminal using awire bond and thermally connected to the base using the die attach.

The adhesive can contact the post and the dielectric layer in the gapand contact the base, the dielectric layer, the routing line, the secondvia and the terminal outside the gap. The adhesive can also cover andsurround the post in the lateral directions and extend to peripheraledges of the assembly. The adhesive can also be coplanar with a top ofthe post. The adhesive can also fill the gap as well as the spacebetween the base and the substrate and be contained in the space betweenthe heat spreader and the substrate.

The post can be integral with the base. For instance, the post and thebase can be a single-piece metal or include a single-piece metal attheir interface. The post can also extend through the aperture. The postcan also be coplanar with the adhesive above the dielectric layer. Thepost can also have a cut-off conical shape in which its diameterdecreases as it extends upwardly from the base to its flat top adjacentto the cap.

The base can be coplanar with the terminal below the adhesive. The basecan also cover the post in the downward direction, support the substrateand be spaced from peripheral edges of the assembly.

The substrate can be spaced from the post and the base. The substratecan also be a laminated structure.

The pad can be an electrical contact for the semiconductor device andthe terminal can be an electrical contact for the next level assemblywhen the semiconductor device is mounted over the heat spreader, oralternatively, the terminal can be an electrical contact for thesemiconductor device and the pad can be an electrical contact for thenext level assembly when the semiconductor device is mounted below theheat spreader. In either case, the pad and the terminal can providevertical signal routing between the semiconductor device and the nextlevel assembly.

The assembly can be a first-level or second-level single-chip ormulti-chip device. For instance, the assembly can be a first-levelpackage that contains a single chip or multiple chips. Alternatively,the assembly can be a second-level module that contains a single LEDpackage or multiple LED packages, and each LED package can contain asingle LED chip or multiple LED chips.

The present invention provides a method of making a semiconductor chipassembly that includes providing a post and a base, mounting an adhesiveon the base including inserting the post through an opening in theadhesive, mounting a substrate on the adhesive including inserting thepost into an aperture in the substrate to form a gap in the aperturebetween the post and the substrate, then flowing the adhesive into andupward in the gap, solidifying the adhesive, then mounting asemiconductor device on a heat spreader that includes the post and thebase, electrically connecting the semiconductor device to the substrateand a terminal below the adhesive, and thermally connecting thesemiconductor device to the heat spreader. The substrate includes firstand second conductive layers and a dielectric layer therebetween and theassembly provides vertical signal routing.

In accordance with an aspect of the present invention, a method ofmaking a semiconductor chip assembly includes (1) providing a post, abase, an adhesive and a substrate, wherein (a) the substrate includes afirst conductive layer, a second conductive layer and a dielectric layertherebetween, (b) the post is adjacent to the base, extends above thebase in an upward direction, extends through an opening in the adhesiveand extends into an aperture in the substrate, (c) the base extendsbelow the post in a downward direction opposite the upward direction andextends laterally from the post in lateral directions orthogonal to theupward and downward directions, (d) the adhesive is mounted on andextends above the base, is sandwiched between the base and the substrateand is non-solidified, (e) the substrate is mounted on and extends abovethe adhesive, the first conductive layer extends above the dielectriclayer, the dielectric layer extends above the second conductive layer,and (f) a gap is located in the aperture between the post and thesubstrate, then (2) flowing the adhesive into and upward in the gap, (3)solidifying the adhesive, then (4) mounting a semiconductor device on aheat spreader that includes the post and the base, wherein thesemiconductor device overlaps or is overlapped by the post, the assemblyincludes a pad, a terminal, a routing line and first and second vias,the pad includes a selected portion of the first conductive layer, therouting line includes a selected portion of the second conductive layer,the first via extends through the dielectric layer between the firstconductive layer and the routing line, the second via extends throughthe adhesive to the routing line, the terminal extends below theadhesive and a heat spreader includes the post and the base, (5)electrically connecting the semiconductor device to the pad or theterminal, thereby electrically connecting the semiconductor device tothe other of the pad and the terminal, wherein an electricallyconductive path between the pad and the terminal includes the first via,the routing line and the second via, and (6) thermally connecting thesemiconductor device to the post or the base, thereby thermallyconnecting the semiconductor device to the other of the post and thebase.

In accordance with another aspect of the present invention, a method ofmaking a semiconductor chip assembly includes (1) providing a post and abase, wherein the post is adjacent to and integral with the base andextends above the base in an upward direction, and the base extendsbelow the post in a downward direction opposite the upward direction andextends laterally from the post in lateral directions orthogonal to theupward and downward directions, (2) providing an adhesive, wherein anopening extends through the adhesive, (3) providing a substrate thatincludes first and second conductive layers and a dielectric layertherebetween, wherein a routing line includes a selected portion of thesecond conductive layer, and an aperture extends through the substrate,(4) mounting the adhesive on the base, including inserting the postthrough the opening, wherein the adhesive extends above the base and thepost extends through the opening, (5) mounting the substrate on theadhesive, including inserting the post into the aperture, wherein thesubstrate extends above the adhesive, the first conductive layer extendsabove the dielectric layer, the dielectric layer extends above thesecond conductive layer, the post extends through the opening into theaperture, the adhesive is sandwiched between the base and the substrateand is non-solidified, and a gap is located in the aperture between thepost and the substrate, then (6) applying heat to melt the adhesive, (7)moving the base and the substrate towards one another, thereby movingthe post upward in the aperture and applying pressure to the moltenadhesive between the base and the substrate, wherein the pressure forcesthe molten adhesive to flow into and upward in the gap and the post andthe molten adhesive extend above the dielectric layer, (8) applying heatto solidify the molten adhesive, thereby mechanically attaching the postand the base to the substrate, then (9) providing a first via thatextends from the first conductive layer through the dielectric layer tothe routing line, (10) providing a second via that extends through theadhesive to the routing line, (11) providing a pad that extends abovethe dielectric layer, including removing selected portions of the firstconductive layer, (12) providing a terminal that extends below theadhesive, including removing selected portions of the base, (13)providing a cap on the post that is above and adjacent to and covers inthe upward direction and extends laterally in the lateral directionsfrom a top of the post, then (14) mounting a semiconductor chip on thecap, wherein a heat spreader includes the post, the base and the cap andthe chip overlaps the post, (15) electrically connecting the chip to thepad, thereby electrically connecting the chip to the terminal, whereinan electrically conductive path between the pad and the terminalincludes in sequence the first via, the routing line and the second via,and (16) thermally connecting the chip to the cap, thereby thermallyconnecting the chip to the base.

Providing the post and the base can include providing a metal plate,forming an etch mask on the metal plate that selectively exposes themetal plate, etching the metal plate in a pattern defined by the etchmask, thereby forming a recess in the metal plate that extends into butnot through the metal plate, and then removing the etch mask, whereinthe post is an unetched portion of the metal plate that protrudes abovethe base and is laterally surrounded by the recess, and the base is anunetched portion of the metal plate below the post and the recess.

Providing the adhesive can include providing a prepreg with uncuredepoxy, flowing the adhesive can include melting the uncured epoxy andcompressing the uncured epoxy between the base and the substrate, andsolidifying the adhesive can include curing the molten uncured epoxy.

Providing the substrate can include providing the routing line,including removing selected portions of the second conductive layer, andthen forming the aperture.

Providing the pad can include grinding the post, the adhesive and thefirst conductive layer such that the post, the adhesive and the firstconductive layer are laterally aligned with one another at a top lateralsurface that faces in the upward direction, and then removing selectedportions of the first conductive layer. The grinding can includegrinding the adhesive without grinding the post and then grinding thepost, the adhesive and the first conductive layer.

Providing the pad can also include removing selected portions of thefirst conductive layer, providing the terminal can include removingselected portions of the base, providing the first via can includeforming a first hole through the first conductive layer and thedielectric layer to the routing line and then depositing a thirdconductive layer into the first hole and on the first conductive layerand the routing line, and providing the second via can include forming asecond hole through the base and the adhesive to the routing line andthen depositing a fourth conductive layer into the second hole and onthe base and the routing line.

Providing the pad, the terminal and the first and second vias can alsoinclude forming the holes, then depositing the third and fourthconductive layers into the holes, and then removing selected portions ofthe first and third conductive layers using a first etch mask thatdefines the pad and removing selected portions of the fourth conductivelayer and the base using a second etch mask that defines the terminal.

Providing the first via can include depositing a third conductive layerinto the first hole and on the post, the first conductive layer, theadhesive and the routing line, providing the second via can includedepositing a fourth conductive layer into the second hole and on thebase, the adhesive and the routing line, providing the pad can includeremoving selected portions of the first and third conductive layers, andproviding the terminal can include removing selected portions of thebase and the fourth conductive layer.

Providing the third and fourth conductive layers can includesimultaneously plating the third and fourth conductive layers, andremoving selected portions of the first, third and fourth conductivelayers and the base can include simultaneously etching the first, thirdand fourth conductive layers and the base.

Providing the heat spreader can include providing a cap on the post thatis above and adjacent to and covers in the upward direction and extendslaterally in the lateral directions from a top of the post aftersolidifying the adhesive and before mounting the semiconductor device.

Providing the cap can include depositing a third conductive layer on thepost after the grinding and removing selected portions of the thirdconductive layer. For instance, providing the cap can include forming anetch mask on the third conductive layer, etching the third conductivelayer using the etch mask to define the cap and then removing the etchmask. Likewise, the pad can be formed by etching the first and thirdconductive layers using the etch mask to define the pad.

Flowing the adhesive can include filling the gap with the adhesive.Flowing the adhesive can also include squeezing the adhesive through thegap, above the post and the substrate and on top surface portions of thepost and the substrate adjacent to the gap.

Solidifying the adhesive can include mechanically bonding the post andthe base to the substrate.

Mounting the semiconductor device can include mounting the semiconductordevice above and overlapping the post, the opening and the aperture.Alternatively, mounting the semiconductor device can include mountingthe semiconductor device below and overlapped by the post, the openingand the aperture.

Mounting and electrically and thermally connecting the semiconductordevice can include mounting the semiconductor device over the post,electrically connecting the semiconductor device to the pad therebyelectrically connecting the semiconductor device to the terminal, andthermally connecting the semiconductor device to the post therebythermally connecting the semiconductor device to the base.Alternatively, mounting and electrically and thermally connecting thesemiconductor device can include mounting the semiconductor device belowthe base, electrically connecting the semiconductor device to theterminal thereby electrically connecting the semiconductor device to thepad, and thermally connecting the semiconductor device to the basethereby thermally connecting the semiconductor device to the post.

Mounting the semiconductor device can include mounting a semiconductorchip on the cap using a die attach, electrically connecting thesemiconductor device can include providing a wire bond between the chipand the pad, and thermally connecting the semiconductor device caninclude providing the die attach between the chip and the cap.Alternatively, mounting the semiconductor device can include mounting asemiconductor chip on the base using a die attach, electricallyconnecting the semiconductor device can include providing a wire bondbetween the chip and the terminal, and thermally connecting thesemiconductor device can include providing the die attach between thechip and the base.

The adhesive can contact the post, the base, the cap, the dielectriclayer, the routing line, the second via and the terminal, cover andsurround the post in the lateral directions and extend to peripheraledges of the assembly after the assembly is manufactured and detachedfrom other assemblies in a batch.

The base can cover the post in the downward direction, extend laterallyfrom the post in the lateral directions and support the substrate afterthe assembly is manufactured and detached from other assemblies in abatch.

The present invention has numerous advantages. The heat spreader canprovide excellent heat spreading and heat dissipation without heat flowthrough the adhesive. As a result, the adhesive can be a low costdielectric with low thermal conductivity and not prone to delamination.The post and the base can be integral with one another, therebyenhancing reliability. The cap can be customized for the semiconductordevice, thereby enhancing the thermal connection. The adhesive can besandwiched between the post and the substrate and between the base andthe substrate, thereby providing a robust mechanical bond between theheat spreader and the substrate. The substrate can provide flexiblemulti-layer signal routing with complex circuitry patterns. The base canprovide mechanical support for the substrate, thereby preventingwarping. The assembly can be manufactured using low temperatureprocesses which reduces stress and improves reliability. The assemblycan also be manufactured using well-controlled processes which can beeasily implemented by circuit board, lead frame and tape manufacturers.

These and other features and advantages of the present invention will befurther described and more readily apparent from a review of thedetailed description of the preferred embodiments which follows.

BRIEF DESCRIPTION OF THE DRAWINGS

The following detailed description of the preferred embodiments of thepresent invention can best be understood when read in conjunction withthe following drawings, in which:

FIGS. 1A-1D are cross-sectional views showing a method of making a postand a base in accordance with an embodiment of the present invention;

FIGS. 1E and 1F are top and bottom views, respectively, corresponding toFIG. 1D;

FIGS. 2A and 2B are cross-sectional views showing a method of making anadhesive in accordance with an embodiment of the present invention;

FIGS. 2C and 2D are top and bottom views, respectively, corresponding toFIG. 2B;

FIGS. 3A-3E are cross-sectional views showing a method of making asubstrate in accordance with an embodiment of the present invention;

FIGS. 3F and 3G are top and bottom views, respectively, corresponding toFIG. 3E;

FIGS. 4A-4M are cross-sectional views showing a method of making athermal board that includes the post, the base, the adhesive and thesubstrate in accordance with an embodiment of the present invention;

FIGS. 4N and 4O are top and bottom views, respectively, corresponding toFIG. 4M;

FIGS. 5A, 5B and 5C are cross-sectional, top and bottom views,respectively, of a semiconductor chip assembly that includes the thermalboard and a semiconductor chip that overlaps the post in accordance withan embodiment of the present invention; and

FIGS. 6A, 6B and 6C are cross-sectional, top and bottom views,respectively, of a semiconductor chip assembly that includes the thermalboard and a semiconductor chip that is overlapped by the post inaccordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1A-1D are cross-sectional views showing a method of making a postand a base in accordance with an embodiment of the present invention,and FIGS. 1E and 1F are top and bottom views, respectively,corresponding to FIG. 1D.

FIG. 1A. is a cross-sectional view of metal plate 10 which includesopposing major surfaces 12 and 14. Metal plate 10 is illustrated as acopper plate with a thickness of 300 microns. Copper has high thermalconductivity, good bondability and low cost. Metal plate 10 can bevarious metals such as copper, aluminum, alloy 42, iron, nickel, silver,gold, combinations thereof, and alloys thereof.

FIG. 1B is a cross-sectional view of etch mask 16 and cover mask 18formed on metal plate 10. Etch mask 16 and cover mask 18 are illustratedas photoresist layers which are deposited on metal plate 10 using dryfilm lamination in which hot rolls simultaneously press photoresistlayers 16 and 18 onto surfaces 12 and 14, respectively. Wet spin coatingand curtain coating are also suitable deposition techniques. A reticle(not shown) is positioned proximate to photoresist layer 16. Thereafter,photoresist layer 16 is patterned by selectively applying light throughthe reticle, applying a developer solution to remove the photoresistportion rendered soluble by the light and then hard baking, as isconventional. As a result, photoresist layer 16 has a pattern thatselectively exposes surface 12, and photoresist layer 18 remainsunpatterned and covers surface 14.

FIG. 1C is a cross-sectional view of recess 20 formed into but notthrough metal plate 10 by etching metal plate 10 in the pattern definedby etch mask 16. The etching is illustrated as a front-side wet chemicaletch. A top spray nozzle (not shown) can spray the wet chemical etch onmetal plate 10 while a bottom spray nozzle (not shown) is deactivated,or the structure can be dipped in the wet chemical etch since cover mask18 provides back-side protection. The wet chemical etch is highlyselective of copper and etches 270 microns into metal plate 10. As aresult, recess 20 extends from surface 12 into but not through metalplate 10, is spaced from surface 14 by 30 microns and has a depth of 270microns. The wet chemical etch also laterally undercuts metal plate 10beneath etch mask 16. A suitable wet chemical etch can be provided by asolution containing alkaline ammonia or a dilute mixture of nitric andhydrochloric acid. Likewise, the wet chemical etch can be acidic oralkaline. The optimal etch time for forming recess 20 withoutexcessively exposing metal plate 10 to the wet chemical etch can beestablished through trial and error.

FIGS. 1D, 1E and 1F are cross-sectional, top and bottom views,respectively, of metal plate 10 after etch mask 16 and cover mask 18 areremoved. The photoresist layers are stripped using a solvent, such as amild alkaline solution with a pH of 9, that is highly selective ofphotoresist with respect to copper.

Metal plate 10 as etched includes post 22 and base 24.

Post 22 is an unetched portion of metal plate 10 defined by etch mask16. Post 22 is adjacent to and integral with and protrudes above base 24and is laterally surrounded by recess 20. Post 22 has a height of 270microns (recess 20 depth), a diameter at its top surface (circularportion of surface 12) of 1000 microns and a diameter at its bottom(circular portion adjacent to base 24) of 1100 microns. Thus, post 22has a cut-off conical shape (resembling a frustum) with taperedsidewalls in which its diameter decreases as it extends upwardly frombase 24 to its flat circular top surface. The tapered sidewalls arisefrom the lateral undercutting by the wet chemical etch beneath etch mask16. The top surface is concentrically disposed within a periphery of thebottom (shown in phantom in FIG. 1E).

Base 24 is an unetched portion of metal plate 10 that is below post 22,extends laterally from post 22 in a lateral plane (with lateraldirections such as left and right) and has a thickness of 30 microns(300−270).

Post 22 and base 24 can be treated to improve bondability to epoxy andsolder. For instance, post 22 and base 24 can be chemically oxidized ormicroetched to provide rougher surfaces.

Post 22 and base 24 are illustrated as a subtractively formedsingle-piece metal (copper). Post 22 and base 24 can also be a stampedsingle-piece metal formed by stamping metal plate 10 with a contactpiece with a recess or hole that defines post 22. Post 22 can also beformed additively, for instance by depositing post 22 on base 24 usingelectroplating, chemical vapor deposition (CVD), physical vapordeposition (PVD) and so on, or semi-additively, for instance bydepositing an upper portion of post 22 on an etch-defined lower portionof post 22. Post 22 can also be sintered to base 24. Post 22 and base 24can also be a multi-piece metal, for instance by electroplating a solderpost 22 on a copper base 24, in which case post 22 and base 24 have ametallurgical interface and are adjacent to but not integral with oneanother.

FIGS. 2A and 2B are cross-sectional views showing a method of making anadhesive in accordance with an embodiment of the present invention, andFIGS. 2C and 2D are top and bottom views, respectively, corresponding toFIG. 2B.

FIG. 2A is a cross-sectional view of adhesive 26. Adhesive 26 isillustrated as a prepreg with B-stage uncured epoxy and a thickness of150 microns.

Adhesive 26 can be various dielectric films or prepregs formed fromnumerous organic or inorganic electrical insulators. For instance,adhesive 26 can initially be a prepreg in which thermosetting epoxy inresin form impregnates a reinforcement and is partially cured to anintermediate stage. The epoxy can be FR-4 although other epoxies such aspolyfunctional and bismaleimide triazine (BT) are suitable. For specificapplications, cyanate esters, polyimide and PTFE are also suitable. Thereinforcement can be E-glass although other reinforcements such asS-glass, D-glass, quartz, kevlar aramid and paper are suitable. Thereinforcement can also be woven, non-woven or random microfiber. Afiller such as silica (powdered fused quartz) can be added to theprepreg to improve thermal conductivity, thermal shock resistance andthermal expansion matching. Commercially available prepregs such asSPEEDBOARD C prepreg by W.L. Gore & Associates of Eau Claire, Wis. aresuitable.

FIGS. 2B, 2C and 2D are cross-sectional, top and bottom views,respectively, of adhesive 26 with opening 28. Opening 28 is a centralwindow that extends through adhesive 26. Opening 28 is formed bymechanical drilling through the prepreg and has a diameter of 1150microns. Opening 28 can be formed by other techniques such as punchingand stamping.

FIGS. 3A-3E are cross-sectional views showing a method of making asubstrate in accordance with an embodiment of the present invention, andFIGS. 3F and 3G are top and bottom views, respectively, corresponding toFIG. 3E.

FIG. 3A is a cross-sectional view of substrate 30 that includes firstconductive layer 32, dielectric layer 34 and second conductive layer 36.First conductive layer 32 contacts and extends above dielectric layer34, second conductive layer 36 contacts and extends below dielectriclayer 34, and dielectric layer 34 contacts and is sandwiched between andis laminated to conductive layers 32 and 36. Conductive layers 32 and 36are electrical conductors and dielectric layer 34 is an electricalinsulator. For instance, conductive layers 32 and 36 are unpatternedcopper sheets with a thickness of 40 microns which is subsequentlyreduced to 30 microns due to photoresist stripping, cleaning and so on,and dielectric layer 34 is epoxy with a thickness of 120 microns.

FIG. 3B is a cross-sectional view of substrate 30 with cover mask 38 andetch mask 40 formed on conductive layers 32 and 36, respectively. Covermask 38 and etch mask 40 are illustrated as photoresist layers similarto photoresist layers 18 and 16, respectively. Photoresist layer 38remains unpatterned and covers first conductive layer 32, andphotoresist layer 40 has a pattern that selectively exposes secondconductive layer 36.

FIG. 3C is a cross-sectional view of substrate 30 with selected portionsof second conductive layer 36 removed by etching second conductive layer36 into a patterned trace layer defined by etch mask 40. The etching isa back-side wet chemical etch similar to the etch applied to metal plate10. First conductive layer 32 remains an unpatterned copper sheet,however the etch etches through second conductive layer 36 to exposedielectric layer 34 and converts second conductive layer 36 from anunpatterned into a patterned layer.

Second conductive layer 36 is shown below dielectric layer 34 to retaina single orientation throughout the figures for ease of comparisonbetween the figures, although in this step the structure may be invertedso that gravity assists the etching.

FIG. 3D is a cross-sectional view of substrate 30 after cover mask 38and etch mask 40 are removed. Photoresist layers 38 and 40 can bestripped in the same manner as photoresist layers 16 and 18.

Second conductive layer 36 as etched includes routing line 42. Thus,routing line 42 is an unetched portion of second conductive layer 36defined by etch mask 40. Furthermore, routing line 42 is a copper tracethat contacts and extends below dielectric layer 34.

FIGS. 3E, 3F and 3G are cross-sectional, top and bottom views,respectively, of substrate 30 with aperture 44. Aperture 44 is a centralwindow that extends through substrate 30. Aperture 44 is formed bymechanical drilling through first conductive layer 32 and dielectriclayer 34 (but not second conductive layer 36 since it was previouslyremoved from this region by the wet chemical etch) and has a diameter of1150 microns. Aperture 44 can be formed with other techniques such aspunching and stamping. Preferably, opening 28 and aperture 44 have thesame diameter and are formed in the same manner with the same drill bitat the same drilling station.

Substrate 30 is illustrated as a laminated structure. Substrate 30 canbe other multi-layer electrical interconnects such as a ceramic board ora printed circuit board. Likewise, substrate 30 can include additionallayers of embedded circuitry.

FIGS. 4A-4M are cross-sectional views showing a method of making athermal board that includes post 22, base 24, adhesive 26 and substrate30 in accordance with an embodiment of the present invention, and FIGS.4N and 4O are top and bottom views, respectively, corresponding to FIG.4M.

FIG. 4A is a cross-sectional view of the structure with adhesive 26mounted on base 24. Adhesive 26 is mounted by lowering it onto base 24as post 22 is inserted into and through and upwards in opening 28.Adhesive 26 eventually contacts and rests on base 24. Preferably, post22 is inserted into and extends though opening 28 without contactingadhesive 26 and is centrally located within opening 28.

FIG. 4B is a cross-sectional view of the structure with substrate 30mounted on adhesive 26. Substrate 30 is mounted by lowering it ontoadhesive 26 as post 22 is inserted into and upwards in aperture 44.Substrate 30 eventually contacts and rests on adhesive 26. Preferably,post 22 is inserted into but not through aperture 44 without contactingsubstrate 30 and is centrally located within aperture 44. As a result,gap 46 is located in aperture 44 between post 22 and substrate 30. Gap46 laterally surrounds post 22 and is laterally surrounded by substrate30. In addition, opening 28 and aperture 44 are precisely aligned withone another and have the same diameter.

At this stage, substrate 30 is mounted on and contacts and extends aboveadhesive 26. Post 22 extends through opening 28 into aperture 44 todielectric layer 34, is 60 microns below the top surface of firstconductive layer 32 and is exposed through aperture 44 in the upwarddirection. Adhesive 26 contacts and is sandwiched between base 24 andsubstrate 30 but is spaced from dielectric layer 34 and remains anon-solidified prepreg with B-stage uncured epoxy, and gap 46 is filledwith air.

FIG. 4C is a cross-sectional view of the structure with adhesive 26 ingap 46. Adhesive 26 is flowed into gap 46 by applying heat and pressure.In this illustration, adhesive 26 is forced into gap 46 by applyingdownward pressure to first conductive layer 32 and/or upward pressure tobase 24, thereby moving base 24 and substrate 30 towards one another andapplying pressure to adhesive 26 while simultaneously applying heat toadhesive 26. Adhesive 26 becomes compliant enough under the heat andpressure to conform to virtually any shape. As a result, adhesive 26sandwiched between base 24 and substrate 30 is compressed, forced out ofits original shape and flows into and upward in gap 46. Base 24 andsubstrate 30 continue to move towards one another and adhesive 26eventually fills gap 46. Moreover, adhesive 26 remains sandwichedbetween and continues to fill the reduced space between base 24 andsubstrate 30.

For instance, base 24 and first conductive layer 32 can be disposedbetween top and bottom platens (not shown) of a press. In addition, atop cull plate and top buffer paper (not shown) can be sandwichedbetween first conductive layer 32 and the top platen, and a bottom cullplate and bottom buffer paper (not shown) can be sandwiched between base24 and the bottom platen. The stack includes the top platen, top cullplate, top buffer paper, substrate 30, adhesive 26, base 24, bottombuffer paper, bottom cull plate and bottom platen in descending order.Furthermore, the stack may be positioned on the bottom platen by toolingpins (not shown) that extend upward from the bottom platen throughregistration holes (not shown) in base 24.

The platens are heated and move towards one another, thereby applyingheat and pressure to adhesive 26. The cull plates disperse the heat fromthe platens so that it is more uniformly applied to base 24 andsubstrate 30 and thus adhesive 26, and the buffer papers disperse thepressure from the platens so that it is more uniformly applied to base24 and substrate 30 and thus adhesive 26. Initially, second conductivelayer 36 is tunnels into and becomes embedded in adhesive 26. As thisoccurs, dielectric layer 34 contacts and presses down on adhesive 26. Asthe platen motion and heat continue, adhesive 26 between base 24 andsubstrate 30 is compressed, melted and flows into and upward in gap 46and across dielectric layer 34 to first conductive layer 32. Forinstance, the uncured epoxy is melted by the heat and the molten uncuredepoxy is squeezed by the pressure into gap 46, however the reinforcementand the filler remain between base 24 and substrate 30. Adhesive 26elevates more rapidly than post 22 in aperture 44 and fills gap 46.Adhesive 26 also rises slightly above gap 46 and overflows onto the topsurfaces of post 22 and first conductive layer 32 adjacent to gap 46before the platen motion stops. This may occur due to the prepreg beingslightly thicker than necessary. As a result, adhesive 26 creates a thincoating on the top surface of post 22. The platen motion is eventuallyblocked by post 22 and the platens become stationary but continue toapply heat to adhesive 26.

The upward flow of adhesive 26 in gap 46 is shown by the thick upwardarrows, the upward motion of post 22 and base 24 relative to substrate30 is shown by the thin upward arrows, and the downward motion ofsubstrate 30 relative to post 22 and base 24 is shown by the thindownward arrows.

FIG. 4D is a cross-sectional view of the structure with adhesive 26solidified.

For instance, the platens continue to clamp post 22 and base 24 andapply heat after the platen motion stops, thereby converting the B-stagemolten uncured epoxy into C-stage cured or hardened epoxy. Thus, theepoxy is cured in a manner similar to conventional multi-layerlamination. After the epoxy is cured, the platens move away from oneanother and the structure is released from the press.

Adhesive 26 as solidified provides a secure robust mechanical bondbetween post 22 and substrate 30 as well as between base 24 andsubstrate 30. Adhesive 26 can withstand normal operating pressurewithout distortion or damage and is only temporarily distorted underunusually high pressure. Furthermore, adhesive 26 can absorb thermalexpansion mismatch between post 22 and substrate 30 and between base 24and substrate 30.

At this stage, post 22 and first conductive layer 32 are essentiallycoplanar with one another and adhesive 26 and first conductive layer 32extend to a top surface that faces in the upward direction. Forinstance, adhesive 26 between base 24 and second conductive layer 36 hasa thickness of 90 microns which is 60 microns less than its initialthickness of 150 microns, post 22 ascends 60 microns in aperture 44 andsubstrate 30 descends 60 microns relative to post 22. The 270 micronheight of post 22 is essentially the same as the combined height offirst conductive layer 32 (30 microns), dielectric layer 34 (120microns), second conductive layer 36 (30 microns) and the underlyingadhesive 26 (90 microns). Furthermore, post 22 continues to be centrallylocated in opening 28 and aperture 44 and spaced from substrate 30, andadhesive 26 fills the space between base 24 and substrate 30 and fillsgap 46. For instance, gap 46 (as well as adhesive 26 between post 22 andsubstrate 30) has a width of 75 microns ((1150−1000)/2) at the topsurface of post 22. Adhesive 26 extends across dielectric layer 34 ingap 46. That is, adhesive 26 in gap 46 extends in the upward anddownward directions across the thickness of dielectric layer 34 at theouter sidewall of gap 46. Adhesive 26 also includes a thin top portionabove gap 46 that contacts the top surfaces of post 22 and firstconductive layer 32 and extends above post 22 by 10 microns.

FIG. 4E is a cross-sectional view of the structure after upper portionsof post 22, adhesive 26 and first conductive layer 32 are removed.

Post 22, adhesive 26 and first conductive layer 32 have their upperportions removed by grinding. For instance, a rotating diamond sandwheel and distilled water are applied to the top of the structure.Initially, the diamond sand wheel grinds only adhesive 26. As thegrinding continues, adhesive 26 becomes thinner as its grinded surfacemigrates downwardly. Eventually the diamond sand wheel contacts post 22and first conductive layer 32 (not necessarily at the same time), and asa result, begins to grind post 22 and first conductive layer 32 as well.As the grinding continues, post 22, adhesive 26 and first conductivelayer 32 become thinner as their grinded surfaces migrate downwardly.The grinding continues until the desired thickness has been removed.Thereafter, the structure is rinsed in distilled water to removecontaminants.

The grinding removes a 25 micron thick upper portion of adhesive 26, a15 micron thick upper portion of post 22 and a 15 micron thick upperportion of first conductive layer 32. The decreased thickness does notappreciably affect post 22 or adhesive 26. However, it substantiallyreduces the thickness of first conductive layer 32 from 30 microns to 15microns.

At this stage, post 22, adhesive 26 and first conductive layer 32 arecoplanar with one another at a smoothed lapped lateral top surface thatis above dielectric layer 34 and faces in the upward direction.

FIG. 4F is a cross-sectional view of the structure with holes 48 and 50.Hole 48 is a blind via that extends through first conductive layer 32and dielectric layer 34 to routing line 42 but is spaced from adhesive26, and hole 50 is a blind via that extends through base 24 and adhesive26 to routing line 42 but is spaced from dielectric layer 34. Holes 48and 50 are formed by laser drilling which may be combined with othertechniques such as mechanical drilling and plasma etching. Holes 48 and50 may have tapered sidewalls and a diameter which decreases with depthbut are shown with vertical sidewalls and a constant diameter forconvenience of illustration.

FIG. 4G is a cross-sectional view of the structure with third conductivelayer 52, fourth conductive layer 54, first via 56 and second via 58.

Third conductive layer 52 is deposited on and contacts post 22, adhesive26 and first conductive layer 32 at the lateral top surface and coversthem in the upward direction. Third conductive layer 52 is anunpatterned copper layer with a thickness of 15 microns and is integralwith first via 56.

Fourth conductive layer 54 is deposited on and contacts base 24 at itsbottom surface and covers it in the downward direction. Fourthconductive layer 54 is an unpatterned copper layer with a thickness of15 microns and is integral with second via 58.

First via 56 extends from first conductive layer 32 into hole 48 and isdeposited on and contacts dielectric layer 34 and routing line 42 inhole 48. First via 56 is a plated through-hole and electrically connectsconductive layers 32 and 52 to routing line 42.

Second via 58 extends from base 24 into hole 50 and is deposited on andcontacts adhesive 26 and routing line 42 in hole 50. Second via 58 is aplated through-hole and electrically connects base 24 and fourthconductive layer 54 to routing line 42.

For instance, the structure is dipped in an activator solution to renderdielectric layer 34 and adhesive 26 at the sidewalls of holes 48 and 50,respectively, catalytic to electroless copper, then a first copper layeris electrolessly plated on post 22, base 24, adhesive 26, firstconductive layer 32, routing line 42 (on opposing surfaces) and thesidewalls of holes 48 and 50, and then a second copper layer iselectroplated on the first copper layer. The first copper layer has athickness of 2 microns, the second copper layer has a thickness of 13microns, and the plated copper layer has a thickness of 15 microns. As aresult, first conductive layer 32 essentially grows and has a thicknessof 40 microns (25+15), which is subsequently reduced to 30 microns dueto photoresist stripping, cleaning and so on. Likewise, base 24essentially grows and has a thickness of 55 microns (30+25), which issubsequently reduced to 45 microns due to photoresist stripping,cleaning and so on.

Thus, third conductive layer 52 serves as a cover layer for post 22 anda build-up layer for first conductive layer 32, and fourth conductivelayer 54 serves as a build-up layer for base 24. Furthermore, vias 56and 58 are formed in holes 48 and 50, respectively. Base 24, conductivelayers 32, 36, 52 and 54 and vias 56 and 58 are shown as a single layerfor convenience of illustration. The boundary (shown in phantom) betweenpost 22 and third conductive layer 52, between base 24 and fourthconductive layer 54 and between conductive layers 32 and 52 may bedifficult or impossible to detect since copper is plated on copper.However, the boundary between adhesive 26 and third conductive layer 52adjacent to post 22 is clear. Likewise, the boundary between dielectriclayer 34 and first via 56 in first hole 48 and between adhesive 26 andsecond via 58 in second hole 50 is clear. Moreover, vias 56 and 58 areshown as posts that fill holes 48 and 50 rather than as hollow tubes forconvenience of illustration.

FIG. 4H is a cross-sectional view of the structure with etch masks 60and 62 formed on the top and bottom surfaces, respectively, of thestructure. Etch masks 60 and 62 are illustrated as photoresist layerssimilar to photoresist layers 16 and 40. Photoresist layer 60 has apattern that selectively exposes third conductive layer 52, andphotoresist layer 62 has a pattern that selectively exposes fourthconductive layer 54.

FIG. 4I is a cross-sectional view of the structure with selectedportions of conductive layers 32 and 52 removed by etching conductivelayers 32 and 52 in the pattern defined by etch mask 60, and selectedportions of base 24 and fourth conductive layer 54 removed by etchingbase 24 and fourth conductive layer 54 in the pattern defined by etchmask 62. The etching is a front-side and back-side wet chemical etchsimilar to the etch applied to metal plate 10. For instance, a top spraynozzle (not shown) and a bottom spray nozzle (not shown) can spray thewet chemical etch on the top and bottom of the structure, or thestructure can be dipped in the wet chemical etch. The wet chemical etchetches through conductive layers 32 and 52 to expose adhesive 26 anddielectric layer 34 and converts conductive layers 32 and 52 from anunpatterned into a patterned layer. The wet chemical etch also etchesthrough base 24 and conductive layer 54 to expose adhesive 26.

FIG. 4J is a cross-sectional view of the structure after etch masks 60and 62 are removed. Photoresist layers 60 and 62 can be stripped in thesame manner as photoresist layers 16 and 18.

Conductive layers 32 and 52 as etched include pad 64 and routing line66, and conductive layer 52 as etched includes cap 68. Pad 64 androuting line 66 are unetched portions of conductive layers 32 and 52defined by etch mask 60, and cap 68 is an unetched portion of conductivelayer 52 defined by etch mask 60. Thus, conductive layers 32 and 52 area patterned layer that includes pad 64 and routing line 66 and excludescap 68. Furthermore, routing line 66 is a copper trace that contacts andextends above dielectric layer 34 and is adjacent to and electricallyconnects first via 56 and pad 64.

Base 24 and conductive layer 54 as etched include base 24, reduced toits central portion and covered by conductive layer 54 in the downwarddirection (base 24/54), and terminal 70. Base 24/54 is an unetchedportion of base 24 and fourth conductive layer 54 defined by etch mask62 and extends laterally beyond post 22 by 1000 microns in the lateraldirections, and terminal 70 is an unetched portion of base 24 and fourthconductive layer 54 defined by etch mask 62 that contacts and extendsbelow adhesive 26. Base 24/54 remains an unpatterned layer, and apatterned layer that is laterally spaced from and outside the peripheryof base 24 includes terminal 70. Thus, terminal 70 is spaced andseparated from and no longer a part of base 24. Furthermore, second via58 is adjacent to terminal 70 and electrically connects routing line 42and terminal 70.

Conductive trace 72 is provided by routing lines 42 and 66, vias 56 and58, pad 64 and terminal 70. Similarly, an electrically conductive pathbetween pad 64 and terminal 70 is in sequence routing line 66, via 56,routing line 42 and via 58 (and vice-versa). Conductive trace 72provides vertical (top to bottom) routing from pad 64 to terminal 70.Conductive trace 72 is not be limited to this configuration. Forinstance, pad 64 can be formed directly above via 56 thereby eliminatingthe need for routing line 66, and via 58 can be electrically connectedto terminal 70 by a routing line below adhesive 26 as defined by etchmask 62. Furthermore, the electrically conductive path can includeadditional vias and routing lines (in the first, second and/oradditional conductive layers) as well as passive components such asresistors and capacitors mounted on additional pads.

Heat spreader 74 includes post 22, base 24/54 and cap 68. Post 22 andbase 24/54 are integral with one another. Cap 68 is above and adjacentto and covers in the upward direction and extends laterally in thelateral directions from the top of post 22. Cap 68 is positioned so thatpost 22 is centrally located within its periphery. Cap 68 also contactsthe underlying portion of adhesive 26 that is coplanar with and adjacentto and laterally surrounds post 22 and covers this portion in the upwarddirection.

Heat spreader 74 is essentially a heat slug with an inverted T-likeshape that includes a pedestal (post 22), wings (base 24/54 portionsthat extend laterally from the pedestal) and a thermal pad (cap 68).

FIG. 4K is a cross-sectional view of the structure with first soldermask 76 formed on dielectric layer 34, third conductive layer 52 and cap68, and second solder mask 78 formed on base 24/54, adhesive 26 andterminal 70.

First solder mask 76 is an electrically insulative layer that isselectively patterned to expose pad 64 and cap 68 and cover routing line66 and the exposed portions of dielectric layer 34 in the upwarddirection. First solder mask 76 has a thickness of 25 microns above pad64 and extends 55 microns (30+25) above dielectric layer 34.

Second solder mask 78 is an electrically insulative layer that isselectively patterned to expose base 24/54 and terminal 70 and cover theexposed portions of adhesive 26 in the downward direction. Second soldermask 78 has a thickness of 25 microns below terminal 70 and extends 70microns (45+25) below adhesive 26.

Solder masks 76 and 78 can initially be a photoimageable liquid resinthat is dispensed on the structure. Thereafter, solder masks 76 and 78are patterned by selectively applying light through reticles (notshown), applying a developer solution to remove the solder mask portionsrendered soluble by the light and then hard baking, as is conventional.

FIG. 4L is a cross-sectional view of the structure with plated contacts80 formed on base 24/54, pad 64, cap 68 and terminal 70.

Plated contacts 80 are thin spot plated metal coatings that contact pad64 and cap 68 and cover their exposed portions in the upward direction,and contact base 24/54 and terminal 70 and cover their exposed portionsin the downward direction. For instance, a nickel layer is electrolesslyplated on base 24/54, pad 64, cap 68 and terminal 70, and then a goldlayer is electrolessly plated on the nickel layer. The buried nickellayer has a thickness of 3 microns, the gold surface layer has athickness of 0.5 microns, and plated contacts 80 have a thickness of 3.5microns.

Base 24/54, pad 64, cap 68 and terminal 70 treated with plated contacts80 as a surface finish have several advantages. The buried nickel layerprovides the primary mechanical and electrical and/or thermalconnection, and the gold surface layer provides a wettable surface tofacilitate solder reflow. Plated contacts 80 also protect base 24/54,pad 64, cap 68 and terminal 70 from corrosion. Plated contacts 80 caninclude a wide variety of metals to accommodate the external connectionmedia. For instance, a silver surface layer plated on a buried nickellayer can accommodate a solder joint or a wire bond.

Base 24/54, pad 64, cap 68 and terminal 70 treated with plated contacts80 are shown as single layers for convenience of illustration. Theboundary (not shown) with plated contacts 80 in base 24/54, pad 64, cap68 and terminal 70 occurs at the copper/nickel interface.

At this stage, the manufacture of thermal board 82 can be consideredcomplete.

FIGS. 4M, 4N and 4O are cross-sectional, top and bottom views,respectively, of thermal board 82 after it is detached at peripheraledges along cut lines from a support frame and/or adjacent thermalboards in a batch.

Thermal board 82 includes base 24/54, adhesive 26, substrate 30,terminal 70, heat spreader 74 and solder masks 76 and 78. Substrate 30includes dielectric layer 34, routing lines 42 and 66, via 56 and pad64. Heat spreader 74 includes post 22, base 24/54 and cap 68. Conductivetrace 72 is provided by routing lines 42 and 66, vias 56 and 58, pad 64and terminal 70.

Post 22 extends through opening 28 and into aperture 44, remainscentrally located within opening 28 and aperture 44 and is coplanar withan adjacent portion of adhesive 26 above dielectric layer 34. Post 22retains its cut-off conical shape with tapered sidewalls in which itsdiameter decreases as it extends upwardly from base 24/54 to its flatcircular top adjacent to cap 68. Base 24/54 covers post 22 in thedownward direction and is spaced from the peripheral edges of thermalboard 82. Cap 68 is above and adjacent to and thermally connected topost 22, covers the top of post 22 in the upward direction and laterallyextends from the top of post 22 in the lateral directions. Cap 68 alsocontacts and covers in the upward direction a portion of adhesive 26that is coplanar with and adjacent to and laterally surrounds post 22.Cap 68 is also coplanar with pad 64.

Adhesive 26 is mounted on and extends above base 24/54, contacts and issandwiched between and fills the space between post 22 and dielectriclayer 34, contacts and is sandwiched between and fills the space betweenbase 24/54 and substrate 30, covers and surrounds post 22 in the lateraldirections and is solidified.

Substrate 30 is mounted on and contacts adhesive 26, extends above theunderlying adhesive 26 and extends above base 24/54, first conductivelayer 32 (as well as pad 64 and routing line 66) contacts and extendsabove dielectric layer 34, dielectric layer 34 contacts and extendsabove second conductive layer 36 (including routing line 42) and issandwiched between conductive layers 32 and 36, and second conductivelayer 36 (including routing line 42) contacts and is embedded inadhesive 26.

Post 22, base 24/54 and cap 68 remain spaced from substrate 30. As aresult, substrate 30 and heat spreader 74 are mechanically attached andelectrically isolated from one another.

Adhesive 26, dielectric layer 34 and solder masks 76 and 78 extend tostraight vertical peripheral edges of thermal board 82 after it isdetached or singulated from a batch of identical simultaneouslymanufactured thermal boards.

Pad 64 is customized as an electrical interface for a semiconductordevice such as a semiconductor chip that is subsequently mounted on cap68, terminal 70 is customized as an electrical interface for the nextlevel assembly such as a printed circuit board that thermal board 82 issubsequently mounted on, cap 68 is customized as a thermal interface forthe semiconductor device, and base 24/54 is customized as a thermalinterface for the printed circuit board. Furthermore, cap 68 isthermally connected to base 24/54 by post 22.

Pad 64 and terminal 70 are vertically offset from one another andexposed at the top and bottom surfaces, respectively, of thermal board82, thereby providing vertical routing between the semiconductor deviceand the next level assembly.

Pad 64 and cap 68 are coplanar with one another at their top surfacesabove dielectric layer 34, and base 24/54 and terminal 70 are coplanarwith one another at their bottom surfaces below adhesive 26.

Conductive trace 72 is shown in cross-section as a continuous circuittrace for convenience of illustration. However, conductive trace 72typically provides horizontal signal routing in both the X and Ydirections. That is, pad 64 and terminal 70 are laterally offset fromone another in the X and Y directions, and routing lines 42 and 66individually or in combination route in the X and Y directions.

Heat spreader 74 provides heat spreading and heat dissipation from asemiconductor device that is subsequently mounted on cap 68 to the nextlevel assembly that base 24/54 is subsequently mounted on. Thesemiconductor device generates heat that flows into cap 68, from cap 68into post 22 and through post 22 into base 24/54 where it is spread outand dissipated in the downward direction, for instance to an underlyingheat sink. Likewise, heat spreader 74 provides heat spreading and heatdissipation from a semiconductor device that is subsequently mounted onbase 24/54 to the next level assembly that cap 68 is subsequentlymounted on.

Thermal board 82 does not expose post 22, vias 56 and 58 or routinglines 42 and 66. Post 22 is covered by cap 68, vias 56 and 58 androuting lines 42 and 66 are covered by solder mask 76, and adhesive 26at its top surface is covered by cap 68 and solder mask 76. Post 22,adhesive 26, vias 56 and 58 and routing lines 42 and 66 are shown inphantom in FIG. 4N for convenience of illustration.

Thermal board 82 includes other conductive traces 72 that typicallyinclude vias 56 and 58, routing lines 42 and 66, pad 64 and terminal 70and have a multi-level electrically conductive path between pad 64 andterminal 70. A single conductive trace 72 is described and labeled forconvenience of illustration. In conductive traces 72, vias 56 and 58,pads 64 and terminals 70 generally have identical shapes and sizeswhereas routing lines 42 and 66 generally have different routingconfigurations. For instance, some conductive traces 72 may be spacedand separated and electrically isolated from one another whereas otherconductive traces 72 can intersect or route to the same pad 64, routingline 42, 66 or terminal 70 and be electrically connected to one another.Likewise, some pads 64 may receive independent signals whereas otherpads 64 share a common signal, power or ground. In addition, someconductive traces 72 may include routing line 42 and vias 56 and 58 toprovide multi-level routing whereas other conductive traces 72 mayexclude routing line 42 and vias 56 and 58 and provide single-levelrouting at first conductive layer 32.

Thermal board 82 can be adapted for multiple chips so that each I/Osignal is routed from a separate pad 64 to a separate terminal 70whereas each ground connection is routed from a separate pad 64 to acommon ground terminal 70.

A brief cleaning step can be applied to the structure at variousmanufacturing stages to remove oxides and debris that may be present onthe exposed metal. For instance, a brief oxygen plasma cleaning step canbe applied to the structure. Alternatively, a brief wet chemicalcleaning step using a solution containing potassium permanganate can beapplied to the structure. Likewise, the structure can be rinsed indistilled water to remove contaminants. The cleaning step cleans thedesired surfaces without appreciably affecting or damaging thestructure.

Advantageously, there is no plating bus or related circuitry that needbe disconnected or severed from conductive traces 72 after they areformed. A plating bus can be disconnected during the wet chemical etchthat forms pad 64, routing line 66, cap 68 and terminal 70.

Thermal board 82 can include registration holes (not shown) that aredrilled or sliced through adhesive 26, substrate 30 and solder masks 76and 78 so that thermal board 82 can be positioned by inserting toolingpins through the registration holes when it is subsequently mounted onan underlying carrier.

Thermal board 82 can omit cap 68. This can be accomplished by adjustingetch mask 60 to expose third conductive layer 52 above all of aperture44 to the wet chemical etch that forms pad 64 and routing line 66.

Thermal board 82 can accommodate multiple semiconductor devices ratherthan one. This can be accomplished by adjusting etch mask 16 to defineadditional posts 22, adjusting adhesive 26 to include additionalopenings 28, adjusting substrate 30 to include additional apertures 44,adjusting etch mask 40 to define additional routing lines 42, adjustingetch masks 60 and 62 to define additional pads 64, routing lines 66,caps 68 and terminals 70 and adjusting solder masks 76 and 78 to containadditional openings. Likewise, substrate 30 can contain additionalrouting lines 42 and vias 56 and 58. The elements except for terminals70 can be laterally repositioned to provide a 2×2 array for foursemiconductor devices. In addition, the topography (lateral shape) canbe adjusted for some but not all of the elements. For instance, pads 64,caps 68 and terminals 70 can retain the same topography whereas routinglines 42 and 66 have different routing configurations.

FIGS. 5A, 5B and 5C are cross-sectional, top and bottom views,respectively, of a semiconductor chip assembly that includes a thermalboard and a semiconductor chip in accordance with an embodiment of thepresent invention.

In this embodiment, the semiconductor device is a chip mounted on thecap. Furthermore, the chip overlaps the post, is electrically connectedto the pad and thereby electrically connected to the terminal and isthermally connected to the cap and thereby thermally connected to thebase.

Semiconductor chip assembly 100 includes thermal board 82, chip 102,wire bond 104, die attach 106 and encapsulant 108. Chip 102 includes topsurface 110, bottom surface 112 and bond pad 114. Top surface 110 is theactive surface and includes bond pad 114 and bottom surface 112 is thethermal contact surface.

Chip 102 is mounted on heat spreader 74, electrically connected tosubstrate 30 and thermally connected to heat spreader 74. In particular,chip 102 is mounted on cap 68, is within the periphery of cap 68,overlaps post 22 but does not overlap substrate 30, is electricallyconnected to substrate 30 by wire bond 104 and is thermally connected toand mechanically attached to heat spreader 74 by die attach 106. Forinstance, wire bond 104 is bonded to and electrically connects pads 64and 114, thereby electrically connecting chip 102 to terminal 70.Likewise, die attach 106 contacts and is sandwiched between andthermally connects and mechanically attaches cap 68 and thermal contactsurface 112, thereby thermally connecting chip 102 to base 24. Pad 64 isspot plated with nickel/silver to bond well with wire bond 104, therebyimproving signal transfer from substrate 30 to chip 102, and cap 68 isshaped and sized to match thermal contact surface 112, thereby improvingheat transfer from chip 102 to heat spreader 74.

Encapsulant 108 is a solid adherent compressible protective plasticenclosure that provides environmental protection such as moistureresistance and particle protection for chip 102 and wire bond 104. Chip102 and wire bond 104 are embedded in encapsulant 108. Furthermore,encapsulant 108 can be transparent if chip 102 is an optical chip suchas an LED. Encapsulant 108 is transparent in FIG. 5B for convenience ofillustration.

Semiconductor chip assembly 100 can be manufactured by mounting chip 102on cap 68 using die attach 106, then wire bonding pads 64 and 114 andthen forming encapsulant 108.

For instance, die attach 106 is initially a silver-filled epoxy pastewith high thermal conductivity that is selectively screen printed on cap68 and then chip 102 placed on the epoxy paste using a pick-up head andan automated pattern recognition system in step-and-repeat fashion.Thereafter, the epoxy paste is heated and hardened at a relatively lowtemperature such as 190° C. to form die attach 106. Next, wire bond 104is a gold wire that is thermosonically ball bonded to pads 64 and 114and then encapsulant 108 is transfer molded on the structure.

Chip 102 can be electrically connected to pad 64 by a wide variety ofconnection media, thermally connected to and mechanically attached toheat spreader 74 by a wide variety of thermal adhesives and encapsulatedby a wide variety of encapsulants.

Semiconductor chip assembly 100 is a first-level single-chip package.

FIGS. 6A, 6B and 6C are cross-sectional, top and bottom views,respectively, of a semiconductor chip assembly that includes a thermalboard and a semiconductor chip in accordance with an embodiment of thepresent invention.

In this embodiment, the chip is mounted on the base rather than the cap.Furthermore, the chip is overlapped by the post, is electricallyconnected to the terminal and thereby electrically connected to the padand is thermally connected to the base and thereby thermally connectedto the cap.

For purposes of brevity, any description of assembly 100 is incorporatedherein insofar as the same is applicable, and the same description neednot be repeated. Likewise, elements of the assembly similar to those inassembly 100 have corresponding reference numerals indexed attwo-hundred rather than one-hundred. For instance, chip 202 correspondsto chip 102, wire bond 204 corresponds to wire bond 104, etc.

Semiconductor chip assembly 200 includes thermal board 82, chip 202,wire bond 204, die attach 206 and encapsulant 208. Chip 202 is invertedand includes (when non-inverted) top surface 210, bottom surface 212 andbond pad 214. Top surface 210 is the active surface and includes bondpad 214 and bottom surface 212 is the thermal contact surface.

Chip 202 is mounted on heat spreader 74, electrically connected tosubstrate 30 and thermally connected to heat spreader 74. In particular,chip 202 is mounted on base 24, is within the periphery of base 24, isoverlapped by post 22 but not overlapped by substrate 30, iselectrically connected to terminal 70 by wire bond 204 and is thermallyconnected to and mechanically attached to heat spreader 74 by die attach206. For instance, wire bond 204 is bonded to and electrically connectspad 214 and terminal 70, thereby electrically connecting chip 202 to pad64. Likewise, die attach 206 is sandwiched between and thermallyconnects and mechanically attaches base 24 and thermal contact surface212, thereby thermally connecting chip 202 to cap 68. Encapsulant 208 istransparent in FIG. 6C for convenience of illustration.

Semiconductor chip assembly 200 can be manufactured by mounting chip 202on base 24 using die attach 206, then wire bonding pad 214 and terminal70 and then forming encapsulant 208.

Semiconductor chip assembly 200 is a first-level single-chip package.

The semiconductor chip assemblies and thermal boards described above aremerely exemplary. Numerous other embodiments are contemplated. Inaddition, the embodiments described above can be mixed-and-matched withone another and with other embodiments depending on design andreliability considerations. For instance, a thermal board with multipleposts for multiple chips can include some conductive traces 72 thatinclude routing lines 42 and 66, vias 56 and 58 and terminal 70 andother conductive traces 72 that exclude routing line 42, vias 56 and 58and do not extend through adhesive 26 or dielectric layer 34. Likewise,the semiconductor device and the cap can overlap the substrate as wellas the underlying adhesive, and the semiconductor device can beoverlapped by the substrate.

The semiconductor device can share or not share the heat spreader withother semiconductor devices. For instance, a single semiconductor devicecan be mounted on the heat spreader. Alternatively, numeroussemiconductor devices can mounted on the heat spreader. For instance,four small chips in a 2×2 array can be attached to the post and thesubstrate can include additional conductive traces to receive and routeadditional wire bonds to accommodate the chips. This may be more costeffective than providing a miniature post for each chip.

The semiconductor chip can be optical or non-optical. For instance, thechip can be an LED, a solar cell, a power chip or a controller chip.Furthermore, the semiconductor device can be mechanically, electricallyand thermally connected to the thermal board using a wide variety ofconnection media including solder and electrically and/or thermallyconductive adhesive.

The heat spreader can provide rapid, efficient and essentially uniformheat spreading and dissipation for the semiconductor device to the nextlevel assembly without heat flow through the adhesive, the substrate orelsewhere in the thermal board. As a result, the adhesive can have lowthermal conductivity which drastically reduces cost. The heat spreadercan be copper and include a post and base that are integral with oneanother and a cap that is metallurgically bonded and thermally connectedto the post, thereby enhancing reliability and reducing cost. The capcan be coplanar with the pad, thereby facilitating the electrical,thermal and mechanical connections with the semiconductor device.Furthermore, when the semiconductor device is above the heat spreader,the cap can be customized for the semiconductor device and the base canbe customized for the next level assembly, thereby enhancing the thermalconnection from the semiconductor device to the next level assembly. Forinstance, the post can have a circular shape in a lateral plane and thecap can have a square or rectangular shape in a lateral plane with thesame or similar topography as the thermal contact of the semiconductordevice Likewise, when the semiconductor device is below the heatspreader, the base can be customized for the semiconductor device andthe cap can be customized for the next level assembly.

The heat spreader can be electrically connected to or isolated from thesemiconductor device and the substrate. For instance, the thirdconductive layer can include a routing line that extends across theadhesive between the substrate and the cap and electrically connects thesemiconductor device to the heat spreader. Thereafter, the heat spreadercan be electrically connected to ground, thereby electrically connectingthe semiconductor device to ground.

The post can be deposited on or integral with the base. For instance,the post can be integral with the base when the post and the base are asingle-piece metal or include a single-piece metal at their interface aswell as additional metal elsewhere. The post can include a flat topsurface or portion. For instance, the post can be coplanar with theadhesive or the post can be etched after the adhesive is solidified toprovide a cavity in the adhesive over the post. The post can also beselectively etched to provide a cavity in the post that extends belowits top surface. In either case, the semiconductor device can be mountedon the post and located in the cavity, and the wire bond can extend intothe cavity to the semiconductor device and out of the cavity to the pad.In this instance, the semiconductor device can be an LED chip and thecavity can focus the LED light in the upward direction.

The base can provide mechanical support for the substrate. For instance,the base can prevent the substrate from warping during metal grinding,chip mounting, wire bonding and encapsulant molding. Furthermore, thebase can include fins at its backside that protrude in the downwarddirection. For instance, the base can be cut at its bottom surface by arouting machine to form lateral grooves that define the fins. In thisinstance, the base can have a thickness of 500 microns, the grooves canhave a depth of 300 microns and the fins can have a height of 300microns. The fins can increase the surface area of the base, therebyincreasing the thermal conductivity of the base by thermal convectionwhen it remains exposed to the air rather than mounted on a heat sink.

The cap can be formed by numerous deposition techniques includingelectroplating, electroless plating, evaporating and sputtering as asingle layer or multiple layers after the adhesive is solidified, eitherbefore, during or after the pad and/or the terminal is formed. The capcan be the same metal as the post. Furthermore, the cap can extendacross the aperture to the substrate or remain within the periphery ofthe aperture. Thus, the cap may contact or be spaced from the substrate.In either case, the cap extends laterally from the top of the post inthe lateral directions.

The adhesive can provide a robust mechanical bond between the heatspreader and the substrate. For instance, the adhesive can fill thespace between the heat spreader and the substrate, the adhesive can belocated in this space and the adhesive can be void-free with consistentbond lines. The adhesive can also absorb thermal expansion mismatchbetween the heat spreader and the substrate. Furthermore, the adhesivecan be a low cost dielectric that need not have high thermalconductivity. Moreover, the adhesive is not prone to delamination. Theadhesive thickness can be adjusted so that the adhesive essentiallyfills the gap and essentially all the adhesive is within structure onceit is solidified and/or grinded. For instance, the optimal prepregthickness can be established through trial and error.

The substrate can provide flexible multi-layer signal routing in the Xand Y directions to provide complex routing patterns. The pad and theterminal can have a wide variety of packaging formats as required by thesemiconductor device and the next level assembly. Furthermore, thesubstrate can be a low cost laminated structure that need not have highthermal conductivity.

The pad and the cap can be coplanar at their top surfaces, therebyenhancing solder joints between the semiconductor device and the thermalboard by controlling solder ball collapse.

The pad and the routing line over the dielectric layer can be formed bynumerous deposition techniques including electroplating, electrolessplating, evaporating and sputtering as a single layer or multiplelayers, either before or after the substrate is mounted on the adhesive.For instance, the first and second conductive layers can be patterned onthe substrate before it is mounted on the adhesive.

The plated contact surface finish can be formed before or after the padand the terminal are formed. For instance, the plated layer can bedeposited on the third and fourth conductive layers and then patternedusing the etch masks that define the pad and the terminal.

The conductive trace can include additional pads, terminals, routinglines and vias as well as passive components and have differentconfigurations. The conductive trace can function as a signal, power orground layer depending on the purpose of the corresponding semiconductordevice pad. The conductive trace can also include various conductivemetals such as copper, gold, nickel, silver, palladium, tin,combinations thereof, and alloys thereof. The preferred composition willdepend on the nature of the external connection media as well as designand reliability considerations. Furthermore, those skilled in the artwill understand that in the context of a semiconductor chip assembly,the copper material can be pure elemental copper but is typically acopper alloy that is mostly copper such copper-zirconium (99.9% copper),copper-silver-phosphorus-magnesium (99.7% copper) andcopper-tin-iron-phosphorus (99.7% copper) to improve mechanicalproperties such as tensile strength and elongation.

The cap, solder masks, plated contacts and third and fourth conductivelayers are generally desirable but may be omitted in some embodiments.

The working format for the thermal board can be a single board ormultiple thermal boards based on the manufacturing design. For instance,a single thermal board can be manufactured individually. Alternatively,numerous thermal boards can be simultaneously batch manufactured using asingle metal plate, a single adhesive, a single substrate and a singletop and bottom solder mask and then separated from one another.Likewise, numerous sets of heat spreaders and conductive traces that areeach dedicated to a single semiconductor device can be simultaneouslybatch manufactured for each thermal board in the batch using a singlemetal plate, a single adhesive, a single substrate and a single top andbottom solder mask.

For example, multiple recesses can be etched in the metal plate to formmultiple posts and the base, then the non-solidified adhesive withopenings corresponding to the posts can be mounted on the base such thateach post extends through an opening, then the substrate (with a singlefirst conductive layer, a single dielectric layer, aperturescorresponding to the posts and underlying routing lines corresponding tothe apertures) can be mounted on the adhesive such that each postextends through an opening into an aperture, then the base and thesubstrate can be moved towards one another by platens to force theadhesive into the gaps in the apertures between the posts and thesubstrates, then the adhesive can be cured and solidified, then theposts, the adhesive and the first conductive layer can be grinded toform a lateral top surface, then the first holes can be formed throughthe first conductive layer and the dielectric layer to the routing linesand the second holes can be formed through the base and the adhesive tothe routing lines, then the third conductive layer can be plated on theposts, the adhesive and the first conductive layer, the fourthconductive layer can be plated on the base, the first vias can be platedin the first holes and the second vias can be plated in the secondholes, then the first and third conductive layers can be etched to formthe pads corresponding to the posts, the third conductive layer can beetched to form the caps corresponding to the posts and the base and thefourth conductive layers can be etched to form the terminalscorresponding to the posts, then the first solder mask can be depositedon the structure and patterned to expose the pads and the caps and thesecond solder mask can be deposited on the structure and patterned toexpose the base and the terminals, then the plated contact surfacefinish can be formed on the base, the pads, the terminals and the capsand then the substrate, the adhesive and the solder masks can be cut orcracked at the desired locations of the peripheral edges of the thermalboards, thereby separating the individual thermal boards from oneanother.

The working format for the semiconductor chip assembly can be a singleassembly or multiple assemblies based on the manufacturing design. Forinstance, a single assembly can be manufactured individually.Alternatively, numerous assemblies can be simultaneously batchmanufactured before the thermal boards are separated from one another.Likewise, multiple semiconductor devices can be electrically, thermallyand mechanically connected to each thermal board in the batch.

For example, die attach paste portions can be deposited on the caps,then the chips can be placed on the die attach paste portions, then thedie attach paste portions can be simultaneously heated and hardened toprovide the die attaches, then the chips can be wired bonded to thecorresponding pads, then the encapsulant can be formed over the chipsand wire bonds, and then the thermal boards can be separated from oneanother.

The thermal boards can be detached from one another in a single step ormultiple steps. For instance, the thermal boards can be batchmanufactured as a panel, then the semiconductor devices can be mountedon the panel and then the semiconductor chip assemblies of the panel canbe detached from one another. Alternatively, the thermal boards can bebatch manufactured as a panel, then the thermal boards of the panel canbe singulated into strips of multiple thermal boards, then thesemiconductor devices can be mounted on the thermal boards of a stripand then the semiconductor chip assemblies of the strip can be detachedfrom one another. Furthermore, the thermal boards can be detached bymechanical sawing, laser sawing, cleaving or other suitable techniques.

The manufacturing process is highly versatile and permits a wide varietyof mature electrical, thermal and mechanical connection technologies tobe used in a unique and improved manner. The manufacturing process canalso be performed without expensive tooling. As a result, themanufacturing process significantly enhances throughput, yield,performance and cost effectiveness compared to conventional packagingtechniques. Moreover, the assembly is well-suited for copper chip andlead-free environmental requirements.

The term “adjacent” refers to elements that are integral (single-piece)or in contact (not spaced or separated from) with one another. Forinstance, the post is adjacent to the base regardless of whether thepost is formed additively or subtractively.

The term “overlap” refers to above and extending within a periphery ofan underlying element. Overlap includes extending inside and outside theperiphery or residing within the periphery. For instance, thesemiconductor device overlaps the post since an imaginary vertical lineintersects the semiconductor device and the post, regardless of whetheranother element such as the cap is between the semiconductor device andthe post and is intersected by the line, and regardless of whetheranother imaginary vertical line intersects the semiconductor device butnot the post (outside the periphery of the post). Likewise, the adhesiveoverlaps the base and the terminal and is overlapped by the pad, and thebase is overlapped by the post. Likewise, the post overlaps and iswithin a periphery of the base. Moreover, overlap is synonymous withover and overlapped by is synonymous with under or beneath.

The term “contact” refers to direct contact. For instance, thedielectric layer contacts the first and second conductive layers butdoes not contact the post or the base.

The term “cover” refers to complete coverage in the upward, downwardand/or lateral directions. For instance, the base covers the post in thedownward direction but the post does not cover the base in the upwarddirection.

The term “layer” refers to patterned and unpatterned layers. Forinstance, the first conductive layer can be an unpatterned blanket sheetand the second conductive layer can be a patterned circuit with spacedtraces when the substrate is mounted on the adhesive, and the firstconductive layer can be a patterned circuit when the semiconductordevice is mounted on the heat spreader. Furthermore, a layer can includestacked layers.

The term “pad” in conjunction with the substrate refers to a connectionregion that is adapted to contact and/or bond to external connectionmedia (such as solder or a wire bond) that electrically connects the padto the semiconductor device when the semiconductor device is above theheat spreader.

The term “terminal” in conjunction with the assembly refers to aconnection region that is adapted to contact and/or bond to externalconnection media (such as solder or a wire bond) that electricallyconnects the terminal to an external device (such as a PCB or a wirethereto) when the semiconductor device is above the heat spreader.

The term “cap” in conjunction with the heat spreader refers to a contactregion that is adapted to contact and/or bond to external connectionmedia (such as solder or thermally conductive adhesive) that thermallyconnects the cap to the semiconductor device when the semiconductordevice is above the heat spreader.

The terms “opening” and “aperture” refer to a through-hole and aresynonymous. For instance, the post is exposed by the adhesive in theupward direction when it is inserted into the opening in the adhesive.Likewise, the post is exposed by the substrate in the upward directionwhen it is inserted into the aperture in the substrate.

The term “inserted” refers to relative motion between elements. Forinstance, the post is inserted into the aperture regardless of whetherthe post is stationary and the substrate moves towards the base, thesubstrate is stationary and the post moves towards the substrate or thepost and the substrate both approach the other. Furthermore, the post isinserted (or extends) into the aperture regardless of whether it is goesthrough (enters and exits) or does not go through (enters withoutexiting) the aperture.

The phrase “move towards one another” also refers to relative motionbetween elements. For instance, the base and the substrate move towardsone another regardless of whether the base is stationary and thesubstrate moves towards the base, the substrate is stationary and thebase moves towards the substrate or the base and the substrate bothapproach the other.

The phrase “mounted on” includes contact and non-contact with a singleor multiple support element(s). For instance, the semiconductor deviceis mounted on the heat spreader regardless of whether it contacts theheat spreader or is separated from the heat spreader by a die attach.Likewise, the semiconductor device is mounted on the heat spreaderregardless of whether it is mounted on the heat spreader alone or theheat spreader and the substrate.

The phrase “adhesive . . . in the gap” refers to the adhesive in thegap. For instance, adhesive that extends across the dielectric layer inthe gap refers to the adhesive in the gap that extends across thedielectric layer. Likewise, adhesive that contacts and is sandwichedbetween the post and the dielectric layer in the gap refers to theadhesive in the gap that contacts and is sandwiched between the post atthe inner sidewall of the gap and the dielectric layer at the outersidewall of the gap.

The term “above” refers to upward extension and includes adjacent andnon-adjacent elements as well as overlapping and non-overlappingelements. For instance, the post extends above, is adjacent to, overlapsand protrudes from the base. Likewise, the post extends above thedielectric layer even though it is not adjacent to or overlap thedielectric layer.

The term “below” refers to downward extension and includes adjacent andnon-adjacent elements as well as overlapping and non-overlappingelements. For instance, the base extends below, is adjacent to, isoverlapped by and protrudes from the post. Likewise, the post extendsbelow the dielectric layer even though it is not adjacent to oroverlapped by the dielectric layer.

The “upward” and “downward” vertical directions do not depend on theorientation of the semiconductor chip assembly (or the thermal board),as will be readily apparent to those skilled in the art. For instance,the post extends vertically above the base in the upward direction andthe adhesive extends vertically below the pad in the downward directionregardless of whether the assembly is inverted and/or mounted on a heatsink. Likewise, the base extends “laterally” from the post in a lateralplane regardless of whether the assembly is inverted, rotated orslanted. Thus, the upward and downward directions are opposite oneanother and orthogonal to the lateral directions, and laterally alignedelements are coplanar with one another at a lateral plane orthogonal tothe upward and downward directions.

The semiconductor chip assembly of the present invention has numerousadvantages. The assembly is reliable, inexpensive and well-suited forhigh volume manufacture. The assembly is especially well-suited for highpower semiconductor devices such as large semiconductor chips whichgenerate considerable heat and require excellent heat dissipation inorder to operate effectively and reliably.

The embodiments described herein are exemplary and may simplify or omitelements or steps well-known to those skilled in the art to preventobscuring the present invention. Likewise, the drawings may omitduplicative or unnecessary elements and reference labels to improveclarity.

Various changes and modifications to the embodiments described hereinwill be apparent to those skilled in the art. For instance, thematerials, dimensions, shapes, sizes, steps and arrangement of stepsdescribed above are merely exemplary. Such changes, modifications andequivalents may be made without departing from the spirit and scope ofthe present invention as defined in the appended claims.

1. A semiconductor chip assembly, comprising: a semiconductor device; anadhesive that includes an opening; a heat spreader that includes a postand a base, wherein the post is adjacent to the base and extends abovethe base in an upward direction, and the base extends below the post ina downward direction opposite the upward direction and extends laterallyfrom the post in lateral directions orthogonal to the upward anddownward directions; a substrate that includes a pad, a routing line, afirst via and a dielectric layer, wherein the pad extends above thedielectric layer, the routing line extends below the dielectric layer,the first via extends through the dielectric layer to the routing line,and an aperture extends through the substrate; a second via that extendsthrough the adhesive to the routing line; and a terminal that extendsbelow the adhesive; wherein an electrically conductive path between thepad and the terminal includes the first via, the routing line and thesecond via; wherein the semiconductor device is mounted on the heatspreader, overlaps or is overlapped by the post, is electricallyconnected to the pad and the terminal, and is thermally connected to thepost and the base; wherein the adhesive is mounted on and extends abovethe base, extends into a gap in the aperture between the post and thesubstrate, extends across the dielectric layer in the gap and issandwiched between the post and the dielectric layer and between thebase and the substrate; wherein the substrate is mounted on the adhesiveand extends above the base, and the routing line is embedded in theadhesive; and wherein the post extends through the opening into theaperture and above the dielectric layer, and the base extends below theadhesive and the substrate.
 2. The assembly of claim 1, wherein thesemiconductor device is a semiconductor chip that overlaps the post, iselectrically connected to the pad and thereby electrically connected tothe terminal, and is thermally connected to the post and therebythermally connected to the base.
 3. The assembly of claim 2, wherein thechip is mounted on the heat spreader using a die attach, electricallyconnected to the pad using a wire bond and thermally connected to thepost using the die attach.
 4. The assembly of claim 2, wherein theadhesive contacts the post and the dielectric layer in the gap andcontacts the base, the dielectric layer, the routing line, the secondvia and the terminal outside the gap.
 5. The assembly of claim 2,wherein the adhesive covers and surrounds the post in the lateraldirections.
 6. The assembly of claim 2, wherein the adhesive fills thegap.
 7. The assembly of claim 2, wherein the adhesive fills the spacebetween the base and the substrate.
 8. The assembly of claim 2, whereinthe adhesive overlaps the terminal.
 9. The assembly of claim 2, whereinthe adhesive extends to peripheral edges of the assembly.
 10. Theassembly of claim 2, wherein the post is integral with the base.
 11. Theassembly of claim 2, wherein the post is coplanar with the adhesiveabove the dielectric layer.
 12. The assembly of claim 2, wherein thepost has a diameter that decreases as it extends upwardly from the baseto its flat top.
 13. The assembly of claim 2, wherein the base iscoplanar with the terminal below the adhesive.
 14. The assembly of claim2, wherein the base covers the post in the downward direction, supportsthe substrate and is spaced from peripheral edges of the assembly. 15.The assembly of claim 2, wherein the substrate is spaced from the postand the base.
 16. The assembly of claim 2, wherein the substrate is alaminated structure.
 17. The assembly of claim 2, wherein the heatspreader includes a cap that extends above and is adjacent to and coversin the upward direction and extends laterally in the lateral directionsfrom a top of the post and that contacts and overlaps the adhesive. 18.The assembly of claim 17, wherein the post, the base and the cap includecopper.
 19. The assembly of claim 17, wherein the cap is coplanar withthe pad above the dielectric layer.
 20. The assembly of claim 17,wherein the cap has a rectangular or square shape and the top of thepost has a circular shape.
 21. A semiconductor chip assembly,comprising: a semiconductor chip; an adhesive that includes an opening;a heat spreader that includes a post, a base and a cap, wherein the postis adjacent to and integral with the base, extends above the base in anupward direction and thermally connects the base and the cap, the baseextends below the post in a downward direction opposite the upwarddirection and extends laterally from the post in lateral directionsorthogonal to the upward and downward directions, and the cap extendsabove and is adjacent to and covers in the upward direction and extendslaterally in the lateral directions from a top of the post; a substratethat includes first and second conductive layers, a first via and adielectric layer, wherein the first conductive layer contacts andextends above the dielectric layer, the second conductive layer contactsand extends below the dielectric layer, a pad includes a selectedportion of the first conductive layer and contacts and extends above thedielectric layer, a routing line includes a selected portion of thesecond conductive layer and contacts and extends below the dielectriclayer, the first via contacts and extends through the dielectric layerbetween the first conductive layer and the routing line, and an apertureextends through the substrate; a second via that contacts and extendsthrough the adhesive to the routing line; and a terminal that contactsand extends below the adhesive; wherein an electrically conductive pathbetween the pad and the terminal includes in sequence the first via, therouting line and the second via; wherein the chip is mounted on the cap,overlaps the post, is electrically connected to the pad and therebyelectrically connected to the terminal, and is thermally connected tothe cap and thereby thermally connected to the base; wherein theadhesive is mounted on and extends above the base, extends into a gap inthe aperture between the post and the substrate, extends across thedielectric layer in the gap, is sandwiched between the post and thedielectric layer in the gap, is sandwiched between the base andsubstrate outside the gap, covers and surrounds the post in the lateraldirections, extends laterally from the post to or beyond the terminaland extends to peripheral edges of the assembly; wherein the substrateis mounted on the adhesive and extends above the base, and the secondconductive layer is embedded in the adhesive; and wherein the postextends through the opening into the aperture and above the dielectriclayer, the cap contacts and overlaps the adhesive and the base extendsbelow the chip, the adhesive and the substrate in the downwarddirection, covers the chip and the post in the downward direction andsupports the substrate.
 22. The assembly of claim 21, wherein the chipis mounted on the cap using a die attach, electrically connected to thepad using a wire bond and thermally connected to the cap using the dieattach.
 23. The assembly of claim 21, wherein the substrate is spacedfrom the post and the base, and the adhesive fills the gap and the spacebetween the base and the substrate and is contained in the space betweenthe heat spreader and the substrate.
 24. The assembly of claim 21,wherein the post has a diameter that decreases as it extends upwardlyfrom the base to the cap.
 25. The assembly of claim 21, wherein the postis coplanar with the adhesive above the dielectric layer, the base iscoplanar with the terminal below the adhesive, the cap is coplanar withthe pad above the dielectric layer and the post, the base and the capinclude copper.
 26. A semiconductor chip assembly, comprising: asemiconductor device; an adhesive that includes an opening; a heatspreader that includes a post and a base, wherein the post is adjacentto and integral with the base and extends above the base in an upwarddirection, and the base extends below the post in a downward directionopposite the upward direction and extends laterally from the post inlateral directions orthogonal to the upward and downward directions; asubstrate that includes a pad, a routing line, a first via and adielectric layer, wherein the pad extends above the dielectric layer,the routing line extends below the dielectric layer, the first viaextends through the dielectric layer to the routing line, and anaperture extends through the substrate; a second via that extendsthrough the adhesive to the routing line; and a terminal that extendsbelow the adhesive; wherein an electrically conductive path between thepad and the terminal includes in sequence the first via, the routingline and the second via; wherein the semiconductor device is mounted onthe heat spreader, overlaps the post, is electrically connected to thepad and thereby electrically connected to the terminal, and is thermallyconnected to the post and thereby thermally connected to the base;wherein the adhesive is mounted on and extends above the base, contactsthe post and the base, extends into a gap in the aperture between thepost and the substrate, extends across the dielectric layer in the gapand is sandwiched between the post and the dielectric layer and betweenthe base and the substrate; wherein the substrate is mounted on theadhesive, extends above the base and is spaced from the post and thebase, and the routing line is embedded in the adhesive; and wherein thepost extends into the opening and the aperture, and the base extendsbelow the adhesive and the substrate.
 27. The assembly of claim 26,wherein the adhesive contacts the post and the dielectric layer in thegap, contacts the dielectric layer, the routing line, the second via andthe terminal outside the gap and extends to peripheral edges of theassembly.
 28. The assembly of claim 26, wherein the post is coplanarwith the adhesive above the dielectric layer.
 29. The assembly of claim26, wherein the heat spreader includes a cap that extends above and isadjacent to and covers in the upward direction and extends laterally inthe lateral directions from a top of the post and the cap contacts andoverlaps the adhesive.
 30. The assembly of claim 29, wherein the cap iscoplanar with the pad above the the adhesive and the dielectric layer,the terminal is coplanar with the base below the adhesive and thedielectric layer and the post is copper, the base, the cap, the pad andthe terminal consist of copper and a plated contact that provides asurface finish on the copper and the cap is copper where it is adjacentto the post.
 31. A semiconductor chip assembly, comprising: asemiconductor device; an adhesive that includes an opening; a heatspreader that includes a post and a base, wherein the post is adjacentto and integral with the base and extends above the base in an upwarddirection, and the base extends below the post in a downward directionopposite the upward direction and extends laterally from the post inlateral directions orthogonal to the upward and downward directions; asubstrate that includes a pad, a routing line, a first via and adielectric layer, wherein the pad extends above the dielectric layer,the routing line extends below the dielectric layer, the first viaextends through the dielectric layer to the routing line, and anaperture extends through the substrate; a second via that extendsthrough the adhesive to the routing line; and a terminal that extendsbelow the adhesive; wherein an electrically conductive path between thepad and the terminal includes in sequence the first via, the routingline and the second via; wherein the semiconductor device is mounted onthe heat spreader, overlaps the post, is electrically connected to thepad and thereby electrically connected to the terminal, and is thermallyconnected to the post and thereby thermally connected to the base;wherein the adhesive is mounted on and extends above the base, extendsinto a gap in the aperture between the post and the substrate, andcontacts and is sandwiched between the post and the dielectric layer inthe gap and between the base and the substrate outside the gap; whereinthe substrate is mounted on the adhesive, extends above the base and isspaced from the post and the base, and the routing line is embedded inthe adhesive; and wherein the post extends into the opening and theaperture, and the base extends below the adhesive and the substrate. 32.The assembly of claim 31, wherein the adhesive contacts the routingline, the second via and the terminal and extends to peripheral edges ofthe assembly.
 33. The assembly of claim 31, wherein the post is coplanarwith the adhesive above the dielectric layer.
 34. The assembly of claim31, wherein the heat spreader includes a cap that extends above and isadjacent to and covers in the upward direction and extends laterally inthe lateral directions from a top of the post and the cap contacts andoverlaps the adhesive.
 35. The assembly of claim 34, wherein the cap iscoplanar with the pad above the dielectric layer, the terminal iscoplanar with the base below the adhesive and the post is copper, thebase, the cap, the pad and the terminal consist of copper and a platedcontact that provides a surface finish on the copper and the cap iscopper where it is adjacent to the post.